TWI808978B - Silicon oxide slurry for polishing liquid composition - Google Patents

Abstract

One aspect of the present invention is a silicon oxide slurry for a polishing liquid composition, which contains silicon oxide particles, a redispersibility improving agent, and water, and the redispersibility improving agent is an alkali thickened polymer emulsion. The silicon oxide slurry for a liquid composition has a pH of not less than 8.0 and not more than 12.0 at 25°C. The average secondary particle size of the silicon oxide particles is preferably not less than 150 nm and not more than 580 nm. The viscosity of the silicon oxide slurry for polishing liquid composition at 25°C is preferably 20 mPa·s or more. When adding an acid or an oxidizing agent to adjust the pH to 0.5 or more and 6.0 or less, the viscosity at 25° C. is preferably 10 mPa·s or less.

Description

Silicon oxide slurry for polishing liquid composition

The invention relates to a silicon oxide slurry for a polishing liquid composition, a polishing liquid set containing the same, and a method for manufacturing the polishing liquid composition. Also, the present invention relates to a method for manufacturing a magnetic disk substrate and a method for polishing the substrate.

In recent years, the miniaturization and the increase in capacity of magnetic disk drives are being developed, and higher recording densities of magnetic disk drives are required. In order to increase the recording density, it is necessary to increase the detection sensitivity of the magnetic signal. Therefore, the industry continues to further reduce the flying height of the magnetic head and the technical development of reducing the unit recording area. For disk substrates, in order to cope with the reduction of the flying height of the magnetic head and ensure the recording area, it is strictly required to improve the smoothness and flatness (reduction of surface roughness, waviness, end face collapse) or the reduction of surface defects (residual abrasive grains, reduction of scratches, protrusions, pits, etc.). In response to such a requirement, from the viewpoint of improving surface quality such as smoother and fewer scratches and improving productivity, the manufacturing method of hard disk substrates often adopts a multi-stage polishing method with two or more polishing steps. Generally speaking, in the final grinding step of the multi-stage grinding method, that is, the fine grinding step, in order to meet the requirements of reducing surface roughness and reducing scratches, protrusions, pits, etc. A polishing liquid composition for processing, and a polishing liquid composition containing alumina particles is used in a polishing step (also referred to as a rough polishing step) prior to a fine polishing step from the viewpoint of improving productivity. However, when alumina particles are used as abrasive grains, there are cases where defects in media and drives are caused due to the penetration of the alumina particles into the substrate.

Therefore, the industry discloses a manufacturing method of a magnetic disk substrate, which can reduce the sticking of the particles to the substrate by using a polishing liquid composition containing silicon oxide particles instead of aluminum oxide particles as abrasive grains in the rough grinding step (Patent Documents 1 to 2).

On the other hand, a polishing liquid composition is disclosed, which is used for polishing the painted surface of automobile paint or building paint, and contains α-alumina with an average particle size of 0.3-3 μm as abrasive particles , containing an alkali-adhesive acrylic polymer as a tackifier (Patent Document 3).

Furthermore, a polishing liquid composition is disclosed, which is a polishing liquid composition for CMP (Chemical Mechanical Polishing, chemical mechanical polishing), and contains cerium oxide particles as abrasive particles, and contains polyacrylic acid ammonium salt as a copolymerization component. A molecular dispersant is used as a dispersant (Patent Document 4). Prior Art Documents Patent Documents

Patent Document 1: Japanese Patent Laid-Open No. 2014-29755 Patent Document 2: Japanese Patent Laid-Open No. 2014-116057 Patent Document 3: Japanese Patent Laid-Open No. 2010-163553 Patent Document 4: Japanese Patent Laid-Open No. 2003-059868 Bulletin

[Problem to be solved by the invention]

If the grinding step of the disk substrate adopts the coarse grinding step and the fine grinding step without using alumina particles, the residue of alumina caused by the adhesion or puncturing of alumina can be suppressed, and the protrusion on the substrate surface after grinding can be reduced. defect. In addition, it was found that when the coarse grinding step is performed with silicon oxide particles having a larger particle size instead of aluminum oxide particles, the problem of poor redispersibility of the precipitated silicon oxide particles in the silicon oxide slurry arises. The deterioration of the redispersibility will lead to the reduction of the polishing speed and the deterioration of the quality of the substrate such as long-period defects. Therefore, it is expected to improve the redispersibility of the silicon oxide particles in the silicon oxide slurry after long-term storage.

Therefore, the present invention provides a silicon oxide slurry for a polishing liquid composition that has excellent redispersibility of silicon oxide particles after long-term storage. Also, the present invention provides a polishing liquid composition capable of ensuring a high polishing rate and ensuring good substrate quality even when using a silicon oxide slurry for a polishing liquid composition that has been stored for a long period of time. [Technical means to solve the problem]

One aspect of the present invention is a silicon oxide slurry for a polishing liquid composition, which contains silicon oxide particles, a redispersibility improving agent, and water, and the redispersibility improving agent is an alkali thickened polymer emulsion. The silicon oxide slurry for a liquid composition has a pH of not less than 8.0 and not more than 12.0 at 25°C.

Another aspect of the present invention is a polishing liquid set, which contains the silicon oxide slurry (first liquid) for the polishing liquid composition of the present invention, and is housed in a material different from the above-mentioned silicon oxide slurry for the polishing liquid composition. The acidic aqueous solution (second liquid) in the other container has a pH of 0.5 to 6.0 at 25°C when the first liquid and the second liquid are mixed.

Another aspect of the present invention is a method for producing a polishing liquid composition, which includes mixing the silicon oxide slurry and acid for the polishing liquid composition of the present invention, and setting the pH value at 25°C to 0.5 or higher And the steps below 6.0.

Another aspect of the present invention is a method for manufacturing a magnetic disk substrate, which includes polishing the substrate to be polished using the polishing liquid composition for magnetic disk substrate prepared by using the silicon oxide slurry for the polishing liquid composition of the present invention. step.

Another aspect of the present invention is a method for polishing a substrate, which includes the step of polishing the substrate to be polished using the polishing liquid composition prepared by using the silicon oxide slurry for the polishing liquid composition of the invention, and the above-mentioned polished substrate It is a substrate used in the manufacture of disk substrates. [Effect of Invention]

According to the present invention, it is possible to provide a silicon oxide slurry for a polishing liquid composition having excellent redispersibility of silicon oxide particles after long-term storage. Therefore, if the silicon oxide slurry for polishing liquid composition of the present invention is used to prepare the polishing liquid composition, then play the following effect: even if use the silicon oxide slurry for polishing liquid composition after long-term preservation also can ensure high polishing Speed and ensure good substrate quality.

The silicon oxide slurry for polishing liquid composition of the present invention (hereinafter sometimes simply referred to as "silicon oxide slurry") is based on the following knowledge, that is, by containing silicon oxide particles as abrasive grains, containing alkali thickening polymer The emulsion is used as a redispersibility enhancer, and the redispersibility of silicon oxide particles after long-term storage is excellent. Also, based on the following insights, that is, since the silicon oxide slurry of the present invention is used in the preparation of the polishing liquid composition of the present invention, even if the polishing liquid composition prepared by using the silicon oxide slurry after long-term preservation is used for Rough grinding can also ensure high grinding speed and good substrate quality.

Generally speaking, as long as the dispersion of silicon oxide particles in the polishing liquid composition used to manufacture magnetic disk substrates is good, not only long-period defects are improved, but other substrate qualities such as long-wavelength fluctuations are also improved. In the present invention, the high polishing rate is ensured, and the adverse effect on substrate quality caused by the use of long-term stored silicon oxide slurry is suppressed, which complement each other and can be expected to improve the productivity of disk substrates.

In the present invention, the details of the mechanism by which silicon oxide particles are excellent in redispersibility, resulting in high polishing rate and good substrate quality are not clear, but are speculated as follows.

In the silicon oxide slurry, silicon oxide particles with relatively large particle diameters precipitate during storage due to their own weight, forming a solid agglomerate layer. When the silicon oxide slurry is stirred and mixed with other components such as acid in order to prepare the polishing liquid composition, if the primary particles of the silicon oxide particles are still firmly agglomerated together, the physical force of the silicon oxide particles becomes difficult. Acting on the concave-convex surface of the substrate to be polished, the polishing speed is reduced, and the particle size of the silicon oxide particles becomes larger, resulting in poor fluctuations or poor removal of long-period defects.

On the other hand, in the present invention, the silica slurry contains an alkali-adhesive polymer emulsion having pH-dependent viscosity switching characteristics, and the pH of the silica slurry at 25° C. is 8.0 to 12.0 Hereinafter, the viscosity switch characteristic refers to the fact that it is hydrated (water-soluble) under alkaline conditions to form a three-dimensional network structure, thereby increasing viscosity, and inhibiting the aggregation of silicon oxide particles due to the three-dimensional network structure, Under acidic conditions, it exists as spheres in water to reduce viscosity. Therefore, even after long-term storage, the redispersibility of the silicon oxide particles in the silicon oxide slurry is good. And, in the case of adding acid etc. to the silicon oxide slurry of the present invention to prepare an acidic polishing liquid composition, because even in the case of using the silicon oxide slurry after long-term storage, the oxidation in the silicon oxide slurry The redispersibility of silicon particles is also good, so the polishing liquid composition can ensure high polishing speed and good substrate quality. Since the alkali viscosity-increasing polymer emulsion has the above-mentioned viscosity switching characteristics, the above-mentioned viscosity increasing caused by the alkali viscosity-increasing polymer emulsion has little adverse effect on the polishing speed in the acidic polishing liquid composition. Since the silicon oxide slurry of the present invention is also contained in the polishing liquid set of the present invention as one liquid, it can ensure both high polishing speed and good substrate quality. However, the present invention is not limited to these mechanisms for interpretation.

In the present invention, the degree of "ensuring a high polishing rate" can be evaluated by using the polishing rate and the rate of decrease in rate when using the polishing liquid composition prepared using the silicon oxide slurry immediately after production. The rate of speed reduction can be calculated, for example, by the method described in the following examples.

That is, the silicon oxide slurry of the present invention contains silicon oxide particles (component a), a redispersibility improving agent (component b), and water, and the redispersibility improving agent (component b) is an alkali thickened polymer emulsion, The pH value of the silicon oxide slurry at 25° C. is not less than 8.0 and not more than 12.0.

In this application, the so-called "undulation" of the substrate refers to the unevenness of the surface of the substrate with a longer wavelength than the roughness. In this application, "long-wavelength fluctuation" refers to fluctuation observed at a wavelength of 500 to 5000 μm. By reducing the long-wavelength fluctuation of the polished substrate surface, the flying height of the magnetic head can be reduced in the magnetic disk drive, and the recording density of the magnetic disk can be increased.

In this application, the so-called "PED (polish enhanced defect, polishing enhanced defect)" refers to a relatively shallow concave-shaped defect that appears on the surface of the substrate after polishing. The PED is produced, for example, during a manufacturing step of a Ni-P plated aluminum alloy substrate. The PED refers to the part of insufficient annealing caused by water or foreign matter attached to the surface of the substrate in the annealing step of the step of coating and forming an aluminum alloy substrate. in the form of defects. The so-called "grinding (Grind) scratch" refers to the scratches of the grinding stone generated in the step of grinding the aluminum alloy substrate before plating. PEDs or grinding damages are also collectively referred to as "long period defects". The generation rate of long-period defects is an index used to evaluate the removal rate of long-period defects, and can be measured using the measuring device described in the examples.

[Silicon Oxide Particles] The silicon oxide slurry of the present invention contains silicon oxide particles (component a) as abrasive grains. From the viewpoint of ensuring a high grinding rate, the silicon oxide particles preferably contain non-spherical silicon oxide particles A (hereinafter, also referred to as "particle A"), in order to ensure both the reduction of long-term defects and the high grinding rate From a viewpoint, it is preferable to contain both the particles A and the spherical silica particles B (hereinafter also referred to as "particles B"). Examples of the silica particles include colloidal silica, fumed silica, precipitated silica, and surface-modified silica.

From the viewpoint of securing a high polishing rate, the particles A are preferably colloidal silica or precipitated silica. In the case where the silicon oxide particles consist only of particle A, the particle A is preferably colloidal silicon oxide from the viewpoint of reducing long-period defects, and when the silicon oxide particles contain both particle A and particle B, it is From the viewpoint of securing a high polishing rate, the particle A is preferably precipitated silicon oxide. Particle A can be one kind of non-spherical silicon oxide particles, or a combination of two or more kinds of non-spherical silicon oxide particles. The particle B is preferably colloidal silicon oxide from the viewpoints of securing a high polishing rate, reducing long-period defects, and reducing protrusion defects. Particle B can be one kind of spherical silicon oxide particles, or a combination of two or more spherical silicon oxide particles.

As a method for producing the particles A, known methods such as the method described on pages 65 to 69 of Tosoh Research and Technology Report, Vol. 45 (2001), can be cited, for example. Specific examples of the method for producing the particles A include a precipitation method in which silicon oxide particles are precipitated by a neutralization reaction between a silicate such as sodium silicate and a mineral acid such as sulfuric acid. It is preferable to carry out the above-mentioned neutralization reaction at relatively high temperature and under alkaline conditions, whereby the growth of the primary particles of silicon oxide proceeds rapidly, and the primary particles aggregate and precipitate in a flocculated form, thereby obtaining the above-mentioned precipitated silicon oxide. Colloidal silica is preferably obtained from water glass or a hydrolyzate of alkoxysilane, more preferably obtained from water glass. Silicon oxide particles obtained from water glass have been produced by known methods.

Particle B can be produced by flame melting method, sol-gel method, and pulverization method, but from the viewpoint of ensuring high grinding speed and reducing long-term defects, and reducing protruding defects after rough grinding and fine grinding From this point of view, silicon oxide particles produced by a particle growth method (hereinafter also referred to as "water glass method") using an alkaline aqueous solution of silicic acid as a starting material are preferable. As the usage form of the particle B, a slurry form is preferable.

The content of the silicon oxide particles (component a) in the silicon oxide slurry of the present invention is preferably at least 10% by mass, more preferably at least 20% by mass, from the viewpoint of improving the redispersibility of the silicon oxide particles. More preferably, it is 30 mass % or more, and, from a viewpoint suitable for manufacture, it is preferable that it is 70 mass % or less, More preferably, it is 60 mass % or less, More preferably, it is 50 mass % or less.

The BET specific surface area of the silicon oxide particles (component a) is preferably 5 m ² /g or more, more preferably 10 m ² /g or more, from the viewpoint of ensuring a high polishing rate and reducing long-period defects , and from the same viewpoint, it is preferably 50 m ² /g or less, more preferably 45 m ² /g or less. Furthermore, when the silicon oxide particles (component a) contain both particle A and particle B, the BET specific surface area of the silicon oxide particles (component a) can be calculated from the BET specific surface area and the blending ratio (mass ratio) of the two particles .

The average primary particle size D1 of the silicon oxide particles (component a) obtained by BET conversion is preferably 50 nm or more, more preferably 70 nm, from the viewpoint of securing a high polishing rate and reducing long-period defects The above, more preferably 90 nm or more, and, from the viewpoint of reducing long-period defects, preferably 300 nm or less, more preferably 250 nm or less, still more preferably 200 nm or less. Furthermore, when the silicon oxide particles (component a) contain both particle A and particle B, D1 of the silicon oxide particles (component a) can be calculated from D1 of the two particles and the compounding ratio (mass ratio).

The average secondary particle diameter D2 of the silicon oxide particles (component a) is preferably 150 nm or more from the viewpoint of securing a high polishing rate and reducing long-period defects, and from the viewpoint of reducing long-period defects. In other words, it is preferably 580 nm or less, more preferably 500 nm or less, further preferably 400 nm or less, and still more preferably 350 nm or less. Furthermore, when the silicon oxide particles (component a) contain both particles A and particles B, D2 of the silicon oxide particles (component a) can be calculated from the D2 of the two particles and the compounding ratio (mass ratio).

(Non-spherical silicon oxide particles) The silicon oxide slurry of the present invention preferably contains non-spherical silicon oxide particles A from the viewpoint of securing a high polishing rate. Particle A can be one kind of non-spherical silicon oxide particles, or can be composed of two or more kinds of non-spherical silicon oxide particles.

The average sphericity of the particles A is preferably at least 0.60, more preferably at least 0.70, from the viewpoint of reducing long-period defects, and from the same viewpoint, is preferably at most 0.85, more preferably at most 0.80 , and more preferably 0.75 or less.

In this application, the average sphericity of particle A is the average value of the sphericity of at least 200 particles A. The sphericity of the particle A can be obtained by obtaining the projected area S and the projected perimeter L of the particle A using, for example, TEM (Transmission Electron Microscopy, transmission electron microscope) observation and image analysis software, and calculated according to the following formula. Sphericity=4π×S/L ² The sphericity of each particle A is the same as the above-mentioned average sphericity, preferably 0.60 or more, more preferably 0.70 or more, and, from the same point of view, preferably 0.85 or less, more preferably 0.80 or less, still more preferably 0.75 or less.

The average short diameter of the particles A is preferably at least 100 nm, more preferably at least 150 nm, and still more preferably at least 180 nm from the viewpoint of ensuring a high polishing rate and reducing long-period defects. From the same viewpoint, it is preferably 500 nm or less, more preferably 450 nm or less.

In the case where the silicon oxide particles (component a) consist only of particle A and the particle A is colloidal silicon oxide, the average short diameter of the particle A is preferable from the viewpoint of ensuring a high polishing rate and reducing long-term defects 100 nm or more, more preferably 150 nm or more, further preferably 180 nm or more, and, from the same viewpoint, preferably 500 nm or less, more preferably 450 nm or less, further preferably 400 nm or less , and more preferably below 300 nm.

When silicon oxide particles (component a) contain both particle A and particle B, and particle A is precipitated silicon oxide, regarding the average short axis of particle A, from the viewpoint of ensuring high polishing rate and reducing long-term defects In other words, it is preferably at least 150 nm, more preferably at least 180 nm, and from the same viewpoint, it is preferably at most 500 nm, and more preferably at most 450 nm.

In this application, the average short diameter of particles A is the average value of the short diameters of at least 200 particles A contained in the silicon oxide slurry of the present invention. The short axis of the particle A is, for example, the length of the short side of the rectangle when the smallest rectangle circumscribing the projected image of the particle A is drawn using, for example, TEM observation and image analysis software. Similarly, the long diameter of the particle A is the length of the long side of the above-mentioned rectangle.

The BET specific surface area of the particles A is preferably 5 m ² /g or more, more preferably 10 m ² /g or more, from the viewpoint of ensuring a high polishing rate and reducing long-period defects. From the standpoint, it is preferably not more than 50 m ² /g, more preferably not more than 40 m ² /g, and still more preferably not more than 30 m ² /g.

In the case where the silicon oxide particles (component a) consist only of particle A and the particle A is colloidal silicon oxide, regarding the BET specific surface area of the particle A, from the viewpoint of securing a high polishing rate and reducing long-period defects, Preferably at least 5 m ² /g, more preferably at least 10 m ² /g, still more preferably at least 20 m ² /g, and from the same viewpoint, preferably at most 50 m ² /g, More preferably, it is 40 m ² /g or less, and still more preferably 30 m ² /g or less.

In the case where silicon oxide particles (component a) contain both particle A and particle B and particle A is precipitated silicon oxide, regarding the BET specific surface area of particle A, the guarantee of high polishing rate and the reduction of long-term defects From a viewpoint, it is preferably at least 5 m ² /g, more preferably at least 10 m ² /g, and, from the same viewpoint, it is preferably at most 50 m ² /g, more preferably at least 40 m ^{2 /} g g or less, more preferably 30 m ² /g or less, still more preferably 20 m ² /g or less.

In the present application, the average primary particle diameter D1 of the particles A can be calculated from the following formula using the BET specific surface area S (m ² /g). Specifically, it can be calculated by the measurement method described in the Example. Average primary particle size (nm) = 2727/S

The average primary particle diameter D1 obtained by BET conversion of the particles A is preferably 50 nm or more, more preferably 70 nm or more, and still more preferably It is 90 nm or more, and from the viewpoint of reducing long-period defects, it is preferably 300 nm or less, more preferably 250 nm or less, and still more preferably 200 nm or less.

In the case where the silicon oxide particles (component a) consist only of particle A and particle A is colloidal silicon oxide, D1 of particle A is preferable from the viewpoint of securing a high polishing rate and reducing long-term defects 50 nm or more, more preferably 70 nm or more, more preferably 90 nm or more, and, from the viewpoint of reducing long-period defects, preferably 300 nm or less, more preferably 250 nm or less, and more preferably 250 nm or less 200 nm or less, more preferably 150 nm or less, further preferably 120 nm or less.

In the case where silicon oxide particles (component a) contain both particle A and particle B and particle A is precipitated silicon oxide, D1 of particle A is from the viewpoint of securing a high polishing rate and reducing long-period defects , preferably not less than 90 nm, more preferably not less than 120 nm, and, from the viewpoint of reducing long-period defects, preferably not more than 300 nm, more preferably not more than 250 nm, and still more preferably not more than 200 nm.

The average secondary particle diameter D2 of the particles A is preferably 150 nm or more from the viewpoint of securing a high polishing rate and reducing long-period defects, and is preferably at least 150 nm from the viewpoint of reducing long-period defects. 580 nm or less, more preferably 500 nm or less, further preferably 400 nm or less, further preferably 350 nm or less.

In the case where the silicon oxide particles (component a) consist only of particle A and particle A is colloidal silicon oxide, D2 of particle A is preferable from the viewpoint of securing a high polishing rate and reducing long-term defects It is 150 nm or more, and from the viewpoint of reducing long-period defects, it is preferably 400 nm or less, more preferably 350 nm or less, further preferably 300 nm or less, and still more preferably 250 nm or less.

When silicon oxide particles (component a) contain both particle A and particle B, and particle A is precipitated silicon oxide, regarding D2 of particle A, from the viewpoint of ensuring high polishing rate and reducing long-period defects , preferably at least 150 nm, more preferably at least 200 nm, further preferably at least 220 nm, further preferably at least 250 nm, and even more preferably at least 300 nm, and from the viewpoint of reducing long-period defects , preferably not more than 580 nm, more preferably not more than 500 nm, further preferably not more than 400 nm, and still more preferably not more than 350 nm.

In this application, the average secondary particle diameter D2 of the particle A refers to the volume-based average particle diameter based on the scattering intensity distribution measured by the light scattering method. In this application, the so-called "scattering intensity distribution" refers to the dynamic light scattering method (DLS: Dynamic Light Scattering) or quasielastic light scattering (QLS: Quasielastic Light Scattering), or static light scattering method (laser diffraction). The volume-converted particle size distribution of particles below the submicron level obtained by the radiation/scattering method. The average secondary particle diameter D2 of the particles A in this application can be obtained specifically by the method described in the examples.

The particle diameter ratio (D2/D1) of the average secondary particle diameter D2 of the particles A to the average primary particle diameter D1 is preferably 1.4 or more from the viewpoint of ensuring a high polishing rate and reducing long-term defects. It is preferably 1.7 or more, and is preferably 4.0 or less, more preferably 3.0 or less, and still more preferably 2.8 or less.

In this application, the particle size ratio (D2/D1) can mean the degree of abnormal shape of the particle A. Usually, the average secondary particle size D2 measured by the light scattering method is processed by detecting the light scattering in the long direction when the particles are irregular particles. Therefore, considering the lengths of the long direction and the short direction, the greater the degree of abnormal shape, The larger the value is. The average primary particle diameter D1 converted from the specific surface area value measured by the BET method is based on the obtained particle volume and expressed in spherical conversion, so it is smaller than the average secondary particle diameter D2 value. From the viewpoint of securing a high polishing rate, the particle diameter ratio (D2/D1) is preferably larger in the above range.

From the viewpoint of securing a high polishing rate and reducing long-period defects, the shape of the particle A is preferably a shape formed by agglomerating a plurality of primary particles.

The content of particle A in the silicon oxide slurry of the present invention is preferably at least 10% by mass, more preferably at least 20% by mass, and still more preferably from the viewpoint of ensuring a high polishing rate and reducing long-term defects. Preferably at least 25% by mass, and, from the viewpoint of economic efficiency, preferably at most 70% by mass, more preferably at most 60% by mass, further preferably at most 50% by mass, still more preferably at most 35% by mass .

(Spherical Silicon Oxide Particles B) As mentioned above, the polishing liquid composition of the present invention preferably further contains spherical silicon oxide particles B (hereinafter, Also referred to as "particle B") as component a, especially when particle A is precipitated silicon oxide, it is preferable to contain particle B from the viewpoint of ensuring a high polishing rate.

In the present application, the average sphericity of particle B is preferably greater than 0.85, more preferably 0.87 or more, and, from the same viewpoint, preferably 1.00 or less, more preferably 0.95 or less. The sphericity of each particle B is preferably greater than 0.85, more preferably not less than 0.87, and is preferably not more than 1.00, more preferably not more than 0.95. The average sphericity and sphericity of particle B can be calculated by the same method as particle A.

From the viewpoint of reducing long-period defects, the average sphericity of particles B is preferably larger than the average sphericity of particles A. The difference between the average sphericity of particles A and B is preferably at least 0.02, more preferably at least 0.05, further preferably at least 0.08, and still more preferably at least 0.1 from the viewpoint of reducing waviness, and from the same viewpoint For , it is preferably 0.50 or less, more preferably 0.40 or less, and still more preferably 0.30 or less.

The average short diameter of particle B is smaller than the average short diameter of particle A. The average short diameter of the particles B is preferably at least 20 nm, more preferably at least 30 nm, and further preferably at least 40 nm from the viewpoint of ensuring a high polishing rate, and from the viewpoint of reducing long-period defects. In other words, it is preferably 200 nm or less, more preferably 150 nm or less, and still more preferably 110 nm or less. The average short axis of particle B can be calculated by the same method as particle A.

Regarding the ratio of the average short diameter of particles A to B in the polishing liquid composition of the present invention (average short diameter of particle A)/(average short diameter of particle B), the guarantee of high polishing speed and the prevention of long-period defects From the viewpoint of reduction, it is preferably 1.3 or more, more preferably 1.5 or more, further preferably 2.0 or more, and even more preferably 2.5 or more, and, from the viewpoint of ensuring a high polishing rate, preferably 13.0 or less, More preferably, it is 10.0 or less, More preferably, it is 8.0 or less, Still more preferably, it is 6.0 or less.

The BET specific surface area of the particles B is preferably at least 5 m ² /g, more preferably at least 10 m 2 /g, and still more preferably at least 20 m ² /g from the viewpoint of securing a high polishing rate and reducing long-term defects. m ² /g or more, and, from the same viewpoint, more preferably 55 m ² /g or less, still more preferably 45 m ² /g or less, still more preferably 35 m ² /g or less.

The average primary particle diameter D1 obtained by BET conversion of the particle B is preferably 20 nm or more, more preferably 30 nm or more, and still more preferably It is 40 nm or more, and from the same viewpoint, it is preferably 150 nm or less, more preferably 120 nm or less, and still more preferably 100 nm or less. The BET-converted average primary particle diameter of particle B can be calculated by the same method as particle A.

The average secondary particle diameter D2 obtained by the dynamic scattering method of the particles B is preferably 20 nm or more, more preferably 30 nm or more, from the viewpoint of ensuring a high polishing rate and reducing long-period defects. It is preferably at least 40 nm, and from the same viewpoint, it is preferably at most 200 nm, more preferably at most 150 nm, and still more preferably at most 120 nm. The average secondary particle diameter of particle B can be calculated by the same measuring method as particle A.

The content of particle B in the silicon oxide slurry of the present invention is preferably at least 5% by mass, more preferably at least 10% by mass, from the viewpoint of securing a high polishing rate and reducing long-period defects, and, From the viewpoint of economic efficiency, it is preferably at most 35% by mass, more preferably at most 30% by mass, further preferably at most 25% by mass.

The mass ratio A/B of particles A to particles B in the silicon oxide slurry of the present invention is preferably 10/90 or more, more preferably 15/85 or more, more preferably 25/75 or more, still more preferably 40/60 or more, and, from the same viewpoint, preferably 99/1 or less, more preferably 90/10 or less, and even more preferably The best is below 75/25. When particle B is a combination of two or more spherical silica particles, the content of particle B refers to the total content of them. The content of particle A is also the same.

When the silicon oxide slurry of the present invention contains silicon oxide particles other than particle A and particle B, regarding the total content of particle A and particle B relative to the whole silicon oxide particles in the silicon oxide slurry, high polishing rate From the viewpoint of securing and reducing long-term defects, it is preferably at least 98.0% by mass, more preferably at least 98.5% by mass, still more preferably at least 99.0% by mass, still more preferably at least 99.5% by mass, and even more preferably It is 99.8 mass % or more, More preferably, it is substantially 100 mass %.

[Redispersibility Improver] The silica slurry of the present invention contains an alkali thickening type polymer emulsion as a redispersibility improver (component b). Alkali viscosity-enhanced polymer emulsions have pH-dependent viscosity switching characteristics. The pH-dependent viscosity switching characteristics mean that if they are under alkaline conditions, they will be hydrated (water-soluble) and adsorbed on silica particles to form a three-dimensional network. Shaped structure, thereby increasing the viscosity, if it exists in the form of spheres in water under acidic conditions, it can reduce the viscosity. Here, "water solubility" means having a solubility of 2 g/100 mL or more in water (20°C).

The silicon oxide slurry of the present invention contains the above-mentioned redispersibility improving agent (ingredient b). Therefore, an acid or the like is added to the silicon oxide slurry of the present invention such that the pH at 25° C. is 0.5 or more and 6.0 or less, When it is preferably not less than 1.0 and not more than 3.0, the viscosity of the silicon oxide slurry at 25°C can be set to preferably not more than 10 mPa·s, more preferably not more than 7.0 mPa·s, still more preferably not more than 5.0 mPa·s s or less, and preferably at least 0.5 mPa·s, more preferably at least 1.0 mPa·s, still more preferably at least 1.5 mPa·s, still more preferably at least 2.0 mPa·s.

As the alkali thickening type polymer emulsion, from the viewpoint of improving the redispersibility of silica particles, it is preferable to be granular in water at a pH of 1.0 to 3.0, and to be granular in water at a pH of 8.0 to 12.0 In the following, the acid group is neutralized to dissolve and diffuse in water, more preferably an alkali-adhesive carboxylic acid-based polymer in which the acid group is a carboxyl group, and more preferably a carboxylic acid-based copolymer. The carboxylic acid-based copolymer is preferably selected from carboxylic acid-based copolymers containing two or more of the following first monomer units, and carboxylic acid-based copolymers containing the following first monomer units and the following second monomer units. At least one polymer in the copolymer is more preferably a carboxylic acid-based copolymer comprising the first monomer unit described below and the second monomer unit described below.

In the case where the alkali-adhesive polymer emulsion is the above-mentioned carboxylic acid-based copolymer, the alkali-adhesive polymer emulsion may only contain the first monomer unit and the second monomer unit as monomer units, but preferably other than In addition to the first monomer unit and the second monomer unit, the following third monomer unit is further contained. As the third unit amount, a cross-linking agent, etc. may be mentioned, and the cross-linking agent is preferably diallyl phthalate having a high viscosity-increasing effect.

Regarding the sum of the mole % of the first monomer unit and the mole % of the second monomer unit relative to the total monomer units contained in the above-mentioned carboxylic acid-based polymer, the guarantee of high polishing rate and the long-term defect From the point of view of the reduction of the mass, it is preferably at least 90% by mass, more preferably at least 94% by mass, and still more preferably at least 98% by mass. From the same point of view, it is preferably at most 100% by mass, more preferably at least 100% by mass. 99.9 mass % or less, More preferably, it is 99.8 mass % or less, More preferably, it is 99.5 mass % or less, More preferably, it is 99.0 mass % or less.

Examples of methods for producing the alkali thickening type polymer emulsion include methods such as emulsion polymerization, suspension polymerization, and solution polymerization. Alkali viscosity-enhanced polymer emulsion is in the state of being neutralized by alkali in water. Examples of the salt include ammonium salts; alkanolamine salts such as triethanolamine; and alkali metal salts such as sodium and potassium; these can be used alone or in combination of two or more.

As the first monomer, it is preferably selected from unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and salts thereof from the viewpoint of improving the redispersibility of silica particles. At least one of them, more preferably at least one selected from acrylic acid, methacrylic acid and their salts. The salt is preferably an alkali metal salt such as an ammonium salt or sodium or potassium.

As the second monomer, monomers other than the above-mentioned unsaturated carboxylic acids and their salts are preferred, such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate (meth)acrylate, etc. base) alkyl acrylate, 2-hydroxyethyl (meth)acrylate, acrylamide, etc. Among them, from the viewpoint of improving the redispersibility of silicon oxide particles, it is preferred to be selected from (methyl) At least one of methyl acrylate and ethyl (meth)acrylate.

Regarding the molar ratio of the first monomer unit and the second monomer unit in the above-mentioned carboxylic acid-based copolymer (mole % of the first monomer unit/mole % of the second monomer unit), the silicon oxide From the viewpoint of particle redispersibility, it is preferably at least 10/90, more preferably at least 20/80, still more preferably at least 30/70, still more preferably at least 35/65, and from the same viewpoint It is preferably 90/10 or less, more preferably 80/20 or less, still more preferably 70/30 or less, further preferably 60/40 or less, further preferably 50/50 or less.

In the above-mentioned carboxylic acid-based polymer, it is preferable that the first monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, and salts thereof, from the viewpoint of improving the redispersibility of the silica particles. The second monomer that forms the carboxylic acid polymer together with the first monomer is preferably at least one selected from alkyl acrylates and alkyl (meth)acrylates, and the third monomer is preferably phthalate Diallyl formate.

The number average molecular weight of the above-mentioned carboxylic acid-based copolymer is preferably at least 500,000 from the viewpoint of improving the redispersibility of silica particles, and from the same viewpoint, it is preferably at most 5 million, and more preferably It is preferably less than 4 million, more preferably less than 3 million. The number average molecular weight can be measured, for example, as follows.

The above number average molecular weight can be measured by the gel permeation chromatography (GPC) method under the following conditions. <GPC conditions> Column: guard column α, analysis column α-M 2 pieces in series Eluent: 60 mmol/L H3PO4, 50 mmol/L LiBr/DMF Flow rate: 1.0 mL/min Column temperature: 40℃ Detection : RI Standard substance: Polystyrene

Specific examples of preferred commercially available products of alkali-adhesive carboxylic acid copolymers include ARON series A-7075, A-7055, B-300K, and B-500 manufactured by Toya Gosei Co., Ltd.; Rohm and PRIMAL TT-615 and TT-935 (both are aqueous emulsions of copolymerized methacrylic acid) manufactured by Haas Co., Ltd.

The mass ratio of the silicon oxide particles in the silicon oxide slurry of the present invention to the redispersibility improving agent is preferably 0.1 by mass relative to 100 parts by mass of the silicon oxide particles from the viewpoint of improving the redispersibility of the silicon oxide particles Part or more, more preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and, from the same viewpoint, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, further preferably 1 part by mass Parts by mass or less.

The content of the redispersibility improving agent in the silicon oxide slurry of the present invention is preferably at least 0.05% by mass, more preferably 0.1% by mass, in terms of solid content conversion, from the viewpoint of improving the redispersibility of the silicon oxide particles. % or more, more preferably 0.15 mass % or more, and, from the viewpoint of economic efficiency, preferably 1.0 mass % or less, more preferably 0.5 mass % or less, still more preferably 0.3 mass % or less.

[Water] The silicon oxide slurry of the present invention contains water as a medium. As water, distilled water, ion-exchanged water, pure water, ultrapure water, etc. are mentioned. The content of water in the silicon oxide slurry is preferably at least 45% by mass, more preferably at least 50% by mass, and still more preferably at least 55% by mass, from the viewpoint of ease of use of the silicon oxide slurry , and from the same viewpoint, it is preferably at most 85% by mass, more preferably at most 80% by mass, and still more preferably at most 75% by mass. Furthermore, it is more preferably at most 70 mass %, and still more preferably at most 65 mass %.

[Other Components] The silicon oxide paste of the present invention may contain other components as needed. Examples of other components include pH adjusters, thickeners, dispersants, rust inhibitors, alkaline substances, polishing rate enhancers, surfactants, polymer compounds, and the like. The above-mentioned other components are preferably contained in the silicon oxide slurry within the range that does not impair the effect of the present invention, and the content of the above-mentioned other components in the silicon oxide slurry is preferably 0% by mass or more, more preferably exceeds 0% by mass, It is further preferably at least 0.01% by mass, still more preferably at least 0.1% by mass, and is preferably at most 10% by mass, more preferably at most 5% by mass.

[pH Adjuster] The pH of the silicon oxide slurry of the present invention is basic from the viewpoint of improving the redispersibility of the silicon oxide particles, and is 8.0 or more and 12.0 or less. When preparing the silicon oxide slurry of the present invention, a pH regulator may also be used as needed. As a pH adjuster, it is a basic compound, for example: Inorganic basic compounds, such as ammonia, potassium hydroxide, and sodium hydroxide; Organic basic compounds, such as an alkylamine and an alkanolamine, etc. are mentioned. Among them, from the viewpoint of improving the redispersibility of silicon oxide particles, at least one selected from ammonia, sodium hydroxide, and alkylamine is preferred, and at least one selected from ammonia and sodium hydroxide is more preferred.

[Alumina Particles] In the silicon oxide slurry of the present invention, from the viewpoint of reducing protrusion defects, the content of alumina particles is preferably at most 0.1% by mass, more preferably at most 0.05% by mass, still more preferably at most 0.02% by mass , and more preferably does not contain alumina particles substantially. In the present invention, the so-called "substantially does not contain alumina particles" may include the following conditions: does not contain alumina particles; does not contain alumina particles in an amount that functions as abrasive grains; amount of alumina particles. The content of alumina particles in the silicon oxide slurry is preferably 2% by mass or less, more preferably 1% by mass or less, further preferably 0.5% by mass or less, relative to the total amount of abrasive grains in the silicon oxide slurry. More preferably, it is substantially 0 mass %.

[pH value] The pH value of the silicon oxide slurry of the present invention is at least 8.0, preferably at least 8.2, more preferably at least 8.5, and still more preferably at least 8.0 from the viewpoint of improving the redispersibility of the silicon oxide particles. 9.0 or more, and, from the same viewpoint, 12.0 or less, preferably 11.0 or less, more preferably 10.8 or less, further preferably 10.5 or less, still more preferably 10.0 or less. Adjustment of pH is preferably carried out by using the above-mentioned pH adjuster. The above pH value is the pH value of the silicon oxide slurry at 25° C., which can be measured with a pH meter, and is preferably the value after immersing the electrode of the pH meter in the polishing liquid composition for 30 seconds.

The viscosity of the silicon oxide slurry of the present invention is preferably at least 20 mPa·s, more preferably at least 50 mPa·s, and still more preferably 100 mPa·s from the viewpoint of improving the redispersibility of the silicon oxide particles. s or more, and, from the same point of view, preferably 10,000 mPa·s or less, more preferably 5,000 mPa·s or less, further preferably 1,000 mPa·s or less, still more preferably 800 mPa·s or less. Viscosity is the value of silicon oxide slurry at 25°C.

[Manufacturing method of polishing liquid composition] The polishing liquid composition of the present invention can, for example, prepare the silicon oxide slurry of the present invention, acid, and further optional oxidizing agents and other components by using known methods, and heat the liquid at 25° C. The pH value is 0.5 to 6.0, preferably 1.0 to 3.0. Therefore, the present invention relates to a method for producing a silicon oxide slurry, which includes at least the steps of preparing silicon oxide particles, a redispersibility enhancer, and water, and the silicon oxide slurry is used to produce a polishing composition. Furthermore, the present invention relates to a method for producing a polishing liquid composition, which includes at least the steps of preparing silicon oxide particles, a redispersibility enhancer, and water, and optionally including adjusting the pH value at 25°C to 0.5 or more and 6.0 Below, preferably a step of 1.0 or more and 3.0 or less.

In the present invention, the so-called "preparation" includes the following situations: mixing silicon oxide particles, redispersibility enhancer and water simultaneously or in any order; mixing silicon oxide slurry, acid, and further oxidizing agents and other The ingredients are mixed simultaneously or in any order. The above preparation can be performed using mixers such as a propeller mixer, a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill, for example. The preferred formulation amount of each component in the manufacturing method of the polishing liquid composition is the same as the preferred content of each component in the polishing liquid composition.

An example of the method for producing the polishing liquid composition of the present invention preferably has the following steps from the viewpoint of the dispersibility of the silicon oxide particles. Step 1: The step of mixing water, acid, any oxidizing agent and other components to adjust the pH value at 25°C to an acidic aqueous solution of 6.0 or less. Step 2: a step of mixing the above acidic aqueous solution with the silicon oxide slurry of the present invention. In step 1, the pH of the obtained acidic aqueous solution is preferably adjusted so that the pH of the polishing liquid composition becomes a desired value, and is preferably 3.0 or less, and is preferably 0.5 or more.

An example of the method for producing the polishing liquid composition of the present invention may include a step of adding water before or after mixing the above-mentioned acidic aqueous solution and the silicon oxide slurry of the present invention. When adding water before mixing the above-mentioned acidic aqueous solution and the silicon oxide slurry of the present invention, water may be added, for example, to the silicon oxide slurry of the present invention. The water may be the water contained in the silicon oxide slurry. Especially when the content of silicon oxide particles in the silicon oxide slurry of the present invention is not less than 10% by mass and not more than 70% by mass, the method for producing the polishing liquid composition of the present invention preferably includes the above-mentioned step of adding water .

[Polishing Liquid Composition] The content of silicon oxide particles in the polishing liquid composition of the present invention is preferably 0.5% by mass or more, more preferably 2% by mass or more, more preferably 3% by mass or more, and, from the viewpoint of economic efficiency, preferably 10% by mass or less, more preferably 8% by mass or less, further preferably 6% by mass or less.

The content of the redispersibility enhancer in the polishing liquid composition of the present invention is preferably at least 0.005% by mass, more preferably at least 0.01% by mass, from the viewpoint of securing a high polishing rate and reducing long-term defects , and more preferably at least 0.02% by mass, and, from the viewpoint of economic efficiency, preferably at most 1.0% by mass, more preferably at most 0.5% by mass, still more preferably at most 0.1% by mass.

[pH value] The pH value of the polishing liquid composition of the present invention at 25° C. is preferably 0.5 or more, more preferably 0.7 or more, and furthermore It is preferably 0.9 or more, more preferably 1.0 or more, still more preferably 1.2 or more, still more preferably 1.4 or more, and, from the same viewpoint, preferably 6.0 or less, more preferably 4.0 or less, and even more preferably 1.2 or more. It is preferably at most 3.0, more preferably at most 2.5, even more preferably at most 2.0. It is preferable to adjust the pH value by using the following acid and, if necessary, an oxidizing agent. The above pH value is the pH value of the polishing liquid composition at 25°C, and the measurement method is the same as that of the silicon oxide slurry.

[Acid] The acid includes, for example, inorganic acids such as nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, sulfamic acid, phosphoric acid, polyphosphoric acid, and phosphonic acid; organic acids such as organic phosphoric acid and organic phosphonic acid; Acid etc. Among them, at least one selected from phosphoric acid, sulfuric acid, and 1-hydroxyethylidene-1,1-diphosphonic acid is preferred, more preferably It is at least one selected from sulfuric acid and phosphoric acid, more preferably phosphoric acid.

The content of the acid in the polishing liquid composition is preferably at least 0.001% by mass, more preferably at least 0.01% by mass, and still more preferably 0.05% by mass, from the viewpoint of securing a high polishing rate and reducing long-term defects. % or more, more preferably 0.1 mass % or more, and, from the same viewpoint, preferably 5.0 mass % or less, more preferably 4.0 mass % or less, further preferably 3.0 mass % or less, and still more preferably 2.5% by mass or less.

[Oxidizing agent] From the viewpoint of securing a high polishing rate and reducing long-term defects, the polishing liquid composition of the present invention may contain an oxidizing agent. Examples of the oxidizing agent include peroxides, permanganic acid or salts thereof, chromic acid or salts thereof, peroxyacids or salts thereof, oxyacids or salts thereof, and the like from the same viewpoint. Among them, preferably at least one selected from hydrogen peroxide, iron (III) nitrate, peracetic acid, ammonium peroxodisulfate, iron (III) and iron ammonium sulfate (III), to ensure a high grinding speed Hydrogen peroxide is more preferable from the viewpoint of metal ions not adhering to the surface of the substrate to be polished, and the viewpoint of easy availability. These oxidizing agents can be used alone or in combination of two or more.

The content of the oxidizing agent in the polishing liquid composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and more preferably 0.1% by mass or more from the viewpoint of ensuring a high polishing rate. From the viewpoint of ensuring the polishing rate and reducing long-term defects, it is preferably at most 4.0% by mass, more preferably at most 2.0% by mass, and still more preferably at most 1.5% by mass.

[Water] The polishing liquid composition of the present invention contains water as a medium. As water, distilled water, ion-exchanged water, pure water, ultrapure water, etc. are mentioned. The content of water in the polishing composition is preferably at least 61% by mass, more preferably at least 70% by mass, and still more preferably at least 80% by mass, from the viewpoint of ease of use of the polishing composition. , and more preferably at least 85% by mass, and, from the same viewpoint, preferably at most 99% by mass, more preferably at most 98% by mass, and still more preferably at most 97% by mass.

[Other Components] The polishing liquid composition of the present invention may contain other components as needed. Examples of other components include thickeners, dispersants, rust inhibitors, alkaline substances, polishing rate enhancers, surfactants, polymer compounds, and the like. The above-mentioned other components are preferably contained in the polishing liquid composition within the range that does not impair the effect of the present invention, and the content of the above-mentioned other components in the polishing liquid composition is preferably 0% by mass or more, more preferably more than 0% by mass, Furthermore, it is preferably at least 0.1% by mass, and is preferably at most 10% by mass, more preferably at most 5% by mass.

In the present invention, "the content of each component in the polishing liquid composition" means the content of each of the above-mentioned components at the point when the polishing liquid composition is used for polishing. Therefore, when the polishing liquid composition of the present invention has been prepared as a concentrate, the content of the above-mentioned components can only be increased by the concentration of each component.

[Viscosity] The viscosity of the polishing liquid composition of the present invention is preferably 10 mPa·s or less, more preferably 7.0 mPa·s or less, from the viewpoint of ensuring a high polishing rate and reducing long-term defects. It is preferably at most 5.0 mPa·s, and, from the same viewpoint, it is preferably at least 0.5 mPa·s, more preferably at least 1.0 mPa·s, still more preferably at least 1.5 mPa·s, still more preferably 2.0 mPa・s or more. The above-mentioned viscosity refers to the viscosity of the polishing liquid composition at 25°C, and the measurement method is the same as that of the silicon oxide slurry.

[Polishing Liquid Set] The polishing liquid set of the present invention is a set for manufacturing a polishing liquid composition, and includes a container-packed silicon oxide slurry containing the above-mentioned silicon oxide slurry containing silicon oxide particles in a container. The polishing liquid set of the present invention may further include an acidic aqueous solution with a pH value of 6.0 or less contained in another container different from the above-mentioned container containing the silicon oxide slurry. According to the present invention, it is possible to provide a polishing liquid set that can obtain a polishing liquid composition capable of ensuring a high polishing rate and reducing long-term defects even when silicon oxide particles are used as abrasive grains.

As the polishing liquid set of the present invention, for example, the following polishing liquid set (two-liquid type polishing liquid composition) can be mentioned: the above-mentioned silicon oxide slurry (first liquid) containing silicon oxide particles, and The acidic aqueous solution (second liquid) of other components in the polishing liquid composition for polishing the object is stored in a state of being unmixed with each other, and these are mixed at the time of use. As a component which can be mix|blended in an acidic aqueous solution, an acid, an oxidizing agent, etc. are mentioned, for example. Arbitrary components may be contained in each of the first liquid and the second liquid as necessary. Examples of the optional components include thickeners, dispersants, rust inhibitors, alkaline substances, polishing rate enhancers, surfactants, polymer compounds, and the like.

[Polished substrate] The polished substrate regarded as the object to be polished by the polishing liquid composition of the present invention is a substrate used to manufacture a magnetic disk substrate, for example, an aluminum alloy substrate plated with Ni-P or silicic acid Glass substrates such as glass, aluminosilicate glass, crystallized glass, and tempered glass are preferably Ni-P-plated aluminum alloy substrates from the viewpoint of cost and ease of use. In the present invention, the so-called "Ni-P-plated aluminum alloy substrate" refers to the one obtained by performing electroless Ni-P plating treatment after grinding the surface of the aluminum alloy base material. After the step of polishing the surface of the substrate to be polished using the polishing liquid composition of the present invention, a step of forming a magnetic layer on the surface of the substrate by sputtering is performed, whereby a magnetic disk can be manufactured. The shape of the polishing substrate includes, for example, a flat surface such as a disc, a plate, a block, and a prism, or a curved surface such as a lens. The substrate to be polished is preferably a disk. In the case of a disc-shaped substrate to be polished, its outer diameter is, for example, 10-120 mm, and its thickness is, for example, 0.5-2 mm.

In general, a magnetic disk is manufactured by polishing a substrate to be polished after a grinding step through a rough grinding step and a finish polishing step, and then passing through a magnetic layer forming step. The polishing liquid composition of the present invention is preferably used for grinding in the coarse grinding step.

[Manufacturing method of magnetic disk substrate] The present invention relates to a method of manufacturing a magnetic disk substrate (hereinafter also referred to as "substrate manufacturing method of the present invention"), which includes using the polishing liquid composition of the present invention to polish the substrate The step of polishing (hereinafter also referred to as "the step of polishing using the polishing liquid composition of the present invention").

In the polishing step using the polishing liquid composition of the present invention, for example, the substrate to be polished is sandwiched by a platen to which a polishing pad is attached, and the polishing liquid composition of the present invention is supplied to the polishing surface, and the surface is rotated while applying pressure. Either one or both of the pad and the substrate to be polished, thereby polishing the substrate to be polished.

Regarding the polishing load in the polishing step using the polishing liquid composition of the present invention, it is preferably 30 kPa or less, more preferably 25 kPa or less, from the viewpoint of reducing long-term defects without greatly impairing the polishing speed, Furthermore, it is preferably 20 kPa or less, and is preferably 3 kPa or more, more preferably 5 kPa or more, and still more preferably 7 kPa or more. In the present invention, the so-called "polishing load" refers to the pressure of the platen applied to the polished surface of the substrate to be polished during polishing. The adjustment of the grinding load can be carried out by the air pressure or vertical load on the platen or substrate.

Regarding the polishing amount per ¹ cm of the substrate to be polished in the polishing step using the polishing liquid composition of the present invention, it is preferably 0.20 mg or more from the viewpoint of reducing long-term defects without greatly impairing the polishing speed , more preferably 0.30 mg or more, further preferably 0.40 mg or more, and, from the same viewpoint, preferably 2.50 mg or less, more preferably 2.00 mg or less, still more preferably 1.60 mg or less.

Regarding the supply rate of the polishing liquid composition per ¹ cm of the substrate to be polished in the polishing step using the polishing liquid composition of the present invention, it is preferably 2.5 mL/min or less from an economical point of view, more preferably 2.0 mL/min or less, more preferably 1.5 mL/min or less, and, from the viewpoint of ensuring a high polishing rate, the supply rate of the polishing liquid composition per 1 cm ² of the substrate to be polished is preferably 0.01 mL/min Above, more preferably at least 0.03 mL/min, still more preferably at least 0.05 mL/min.

As a method of supplying the polishing liquid composition of this invention to a grinder, the method of supplying continuously using a pump etc. is mentioned, for example. When supplying the polishing liquid composition to the polishing machine, in addition to the method of supplying it in the form of one liquid containing all the components, considering the storage stability of the polishing liquid composition, etc., it can also be divided into multiple preparation liquids, and It is supplied in the form of more than 2 liquids. In the latter case, for example, in a supply pipe or on a substrate to be polished, the above-mentioned plurality of preparation component liquids are mixed to obtain the polishing liquid composition of the present invention.

According to the substrate manufacturing method of the present invention, the following effect can be exerted: long-period defects can be reduced without greatly impairing the polishing speed during rough polishing, so that a magnetic disk substrate with reduced protrusion defects can be manufactured efficiently.

[Grinding method] The present invention relates to a polishing method of a magnetic disk substrate (hereinafter also referred to as the polishing method of the present invention), which includes a polishing step using the polishing liquid composition of the present invention.

By using the polishing method of the present invention, the following effect can be exerted: the long-period defects can be reduced without greatly impairing the polishing speed in the rough polishing, so that the productivity of the magnetic disk substrate with reduced protrusion defects can be improved. The specific polishing method and conditions can be set to be the same as the substrate manufacturing method of the present invention described above. [Example]

Hereinafter, the present invention will be described in further detail by means of examples, but these are illustrative, and the present invention is not limited to these examples.

1. Preparation of abrasive slurry using the abrasive grains in Table 1 (non-spherical silica particles A1-A3, non-spherical alumina particles A4, spherical silica particles B1), and the redispersibility enhancer in Table 3 ( Component b) or its comparison object, and water prepared the abrasive grain slurries of Examples 1-14 and Comparative Examples 1-7. Regarding the content of each component in the abrasive grain slurry, abrasive grains: 30-50% by mass (A1: 40% by weight, A2: 40% by weight, A3: 30% by weight, A4: 45% by weight, B1: 50% by weight %), redispersibility enhancer (ingredient b) or its comparative object: the amount recorded in Table 3, and the balance is water. The pH value of the abrasive slurry in Examples 1-14 and Comparative Examples 1-7 was 10 at 25°C. Furthermore, the details of Particle A and Particle B are as described in Table 1.

The non-spherical silicon oxide particles A1 and A2 are colloidal silicon oxide, the non-spherical silicon oxide particle A3 is precipitated silicon oxide, and the particle B is colloidal silicon oxide produced by the water glass method. The pH of the abrasive slurry was measured using a pH meter (manufactured by Toa DKK Co., Ltd.), and the value obtained after immersing the electrode in the polishing liquid composition for 30 seconds was used (the same applies hereinafter).

A-7075, A-7055, B-500, and B-300K in Table 3 are all alkali viscosity-increasing polymer emulsions, and are carboxylic acid copolymers, all of which contain the first monomer unit and the second monomer unit .

[Table 1]

2. Preparation of Polishing Liquid Composition [Preparation of Polishing Liquid Composition for Rough Polishing] An acidic aqueous solution (pH=1.5) was adjusted by mixing an acid (phosphoric acid), an oxidizing agent (hydrogen peroxide) and water. After the preparation of the abrasive grain slurry prepared by the method described in "1. Preparation of abrasive grain slurry", immediately or after standing for 3 months, the abrasive grains of Examples 1-14 and Comparative Examples 1-7 were ground The granular slurry and the acidic aqueous solution were mixed to prepare polishing liquid compositions 1-21. The contents of each component in the polishing liquid compositions 1 to 21 are abrasive grains: 5.0% by mass, redispersibility enhancer (component b) or its comparative object: the amount described in Table 3, phosphoric acid: 1.5% by mass %, hydrogen peroxide: 0.8% by mass. The balance is water. The pH value of the polishing liquid compositions 1-21 at 25° C. was 1.6.

[Preparation of Polishing Liquid Composition C for Fine Polishing] Using the colloidal silica particles (abrasive grain a) in Table 2, sulfuric acid, hydrogen peroxide, and water, Polishing liquid composition C for fine polishing was prepared. The contents of each component in the polishing liquid composition C were colloidal silica particles: 5.0% by mass, sulfuric acid: 0.5% by mass, and hydrogen peroxide: 0.5% by mass. The pH of the polishing liquid composition C is 1.4. This polishing liquid composition C was used in the finishing step described below. The detailed content of abrasive grain a is as described in Table 2.

[Table 2]

3. Measuring method of each parameter [Measuring method of BET specific surface area of abrasive grain] BET specific surface area S is after performing the following [pretreatment], and accurately weighs about 0.1 g of the sample in the measuring unit until the decimal point The last 4 digits (0.1 mg digits) were dried in an atmosphere of 110°C for 30 minutes immediately before the measurement of the specific surface area, and then used a specific surface area measuring device (Shimadzu Corporation's microcrystalline granular automatic specific surface area measuring device "Flowsorb III2305") ), and measured by BET method. [Pretreatment] Take the slurry-like particles into a petri dish, and dry them in a hot air dryer at 150°C for 1 hour. The dried sample was pulverized finely with an agate mortar to obtain a measurement sample.

[Measuring method of BET specific surface area and average primary particle diameter D1 of abrasive grains] The average primary particle diameter (nm) of abrasive grains is calculated using the specific surface area S (m ² /g) by the BET (nitrogen adsorption) method. Calculated by the following formula. (1) Average primary particle size of silicon oxide particles (nm) = 2727/S = 6/(ρ×S) ρ: density of substance (kg/m ³ ) (2) Average primary particle size of alumina particles (nm ) = 1508/S

[Measurement method of average secondary particle size of abrasive grains] (1) Measurement method of average secondary particle size of silicon oxide particles A1, A2, B1 Dilute silicon oxide particles with ion-exchanged water to prepare silicon oxide containing 1% by mass particle dispersion. Then, this dispersion liquid was put into the measuring device described below, and the volume particle size distribution of the silicon oxide particles was obtained. The particle diameter (Z-average value) at which the cumulative volume frequency of the obtained volume particle size distribution becomes 50% was defined as the secondary particle diameter. Measuring machine: Malvern, Zetasizer Nano "Nano S" Measuring conditions: Sample volume 1.5 mL: Laser He-Ne, 3.0 mW, 633 nm: Scattered light detection angle 173°

(2) Measuring method of average secondary particle diameter of silicon oxide particles A3 (2-1) Silicon oxide particles A3 Put water as a dispersion medium into the following measuring device, and then make the transmittance 75 to 95% A sample (silicon oxide particle A3) was put in, and after applying ultrasonic waves for 5 minutes, the particle diameter was measured. (2-2) Alumina particles A4 An aqueous solution containing 0.5% by mass of POIZ 530 (manufactured by Kao Corporation, a polycarboxylic acid polymer surfactant) was used as a dispersion medium and put into the following measuring device, and then the transmittance A sample (alumina particle 4A) was thrown in so as to become 75 to 95%, and after applying ultrasonic waves for 5 minutes thereafter, the particle diameter was measured. Measuring machine: Laser diffraction/scattering type particle size distribution measuring device LA920 manufactured by Horiba Manufacturing Co., Ltd. Cycle intensity: 4 Ultrasonic intensity: 4

[Measuring method of average minor diameter and average sphericity of abrasive grains] Observe abrasive grains with TEM ("JEM-2000FX" manufactured by JEOL Ltd., 80 kV, 10,000-50,000 times) and use a scanner to take the pictures obtained from the observation Input the image data into a personal computer, and analyze the projected image of 500 abrasive grains using analysis software (Mitani Corporation "WinROOF (Ver.3.6)") as follows. The short diameter of each abrasive grain was calculated, and the average value of the short diameters (average short diameter) was obtained. Furthermore, the sphericity of each abrasive grain was calculated from the area S and the circumference L of each abrasive grain according to the following formula, and the average value of the sphericity (average sphericity) was obtained. Sphericity=4π×S/L ²

[D10, D50, and D90 of abrasive grain a] The 1% by mass dispersion liquid obtained by diluting abrasive grain a with ion-exchanged water was put into the following measurement device to obtain the volume particle size distribution of silicon oxide abrasive grains. Measuring machine: Malvern, Zetasizer Nano "Nano S" Measuring conditions: Sample volume 1.5 mL: Laser He-Ne, 3.0 mW, 633 nm: Scattered light detection angle 173° And, the cumulative volume frequency of the obtained volume particle size distribution The particle sizes at which 10%, 50%, and 90% are obtained are set to D10, D50 (volume average particle size), and D90, respectively.

4. Redispersibility The redispersibility of silicon oxide particles in silicon oxide slurry is evaluated by precipitation rate (%). The sedimentation rate is the ratio of the sedimentation amount (g) relative to the total solid content when the total solid content is assumed to be 100. The silica slurry prepared and left standing for 3 months was vibrated with a vibrator ("MW-YS" manufactured by Miyamoto Riken Industry Co., Ltd.) for 30 seconds at a rotation speed of 100 rpm. The supernatant was removed and the remaining Set as precipitation amount. The smaller the precipitation rate, the better the redispersibility of the silicon oxide slurry. [Evaluation criteria] A: Sedimentation rate of 0% or more and less than 1% B: Sedimentation rate of 1% or more and less than 3% C: Sedimentation rate of 3% or more

5. Grinding conditions Grinding the substrate to be polished is carried out according to the following steps (1) to (3). The conditions of each step are shown below. Step (3) is performed using a grinder different from that used in step (1). (1) Rough polishing step: a step of polishing the surface to be polished of the substrate to be polished using the polishing liquid compositions 1 to 21. (2) Cleaning step: a step of cleaning the substrate obtained in step (1). (3) Fine polishing step: a step of polishing the surface to be polished of the substrate obtained in step (2) using the polishing liquid composition C.

[Substrate to be polished] The substrate to be polished is an aluminum alloy substrate plated with Ni-P. The substrate to be polished has a thickness of 1.27 mm and a diameter of 95 mm.

[Step (1): Coarse grinding] Grinder: double-sided grinder (9B type double-sided grinder, manufactured by SpeedFam Co., Ltd.) Number of substrates to be polished: 10 pieces Polishing liquid: polishing liquid composition 1 to 21 Polishing pad: suede type (Foaming layer: polyurethane elastomer), thickness: 1.0 mm, average pore diameter: 30 μm, compressibility of surface layer: 2.5% (manufactured by Filwel Co.) Platen rotation speed: 35 rpm Grinding load: 9.8 kPa (set value) Supply rate of polishing liquid: 100 mL/min (equivalent to 0.076 mL/min per 1 cm ² of the substrate surface to be polished) Grinding time: 6 minutes

[Step (2): Cleaning] The substrate obtained in step (1) was cleaned under the following conditions. First, the substrate obtained in the step (1) was immersed for 5 minutes in a tank containing an alkaline cleaning agent composition with a pH value of 12 containing 0.1 mass % potassium hydroxide (KOH) aqueous solution. Next, rinse the dipped substrate for 20 seconds with ion-exchanged water. Then, the rinsed substrate is transferred to a scrubbing unit equipped with cleaning brushes for cleaning.

[Step (3): Fine Grinding] Grinding machine: double-sided grinding machine (9B type double-sided grinding machine, manufactured by SpeedFam Company), a grinding machine different from the grinding machine used in step (1) Number of substrates to be ground: 10 pieces Polishing liquid: Polishing liquid composition C Polishing pad: suede type (foam layer: polyurethane elastomer), thickness: 0.9 mm, average pore diameter: 5 μm, compressibility of the surface layer: 10.2% ( Manufactured by Fujibo Corporation) Platen rotation speed: 40 rpm Grinding load: 9.8 kPa Grinding liquid supply rate: 100 mL/min (equivalent to 0.076 mL/min per 1 cm ² of the surface of the substrate to be polished) Grinding time: 2 minutes in step ( 3) After cleaning. The cleaning conditions are carried out under the same conditions as in the above step (2).

6. Evaluation method [Measuring method and evaluation of polishing speed in step (1)] Measure the weight of each substrate before and after polishing, and use (manufactured by Sartorius, "BP-210S") to measure, according to the mass of each substrate Change to find the amount of mass reduction. The value obtained by dividing the average mass loss of all 10 sheets by the polishing time was defined as the polishing rate, and calculated by the following formula. The results are shown in Table 3. Mass loss (g) = {mass before grinding (g) - mass after grinding (g)} Grinding speed (mg/min) = mass loss (mg) / grinding time (min)

Moreover, the rate of speed reduction (%) was calculated by the following formula, and the result is shown in Table 3. Speed reduction rate (%) = 100 - grinding speed after standing for 3 months ÷ grinding speed immediately after manufacture × 100 Speed reduction rate: evaluation -5% or more and less than 5%: "A: excellent grinding speed, can Looking forward to further increase in substrate yield" More than 5% and less than 10%: "B: The polishing speed is good, and an increase in substrate yield can be expected" More than 10%: "C: Need to improve in actual production"

[Evaluation method for long-period defects on substrate surface after step (1)] For both sides of 10 substrates (total 20 locations) after step (1) polishing, perform step (2) and measure under the following conditions And the production rate (%) was calculated|required. Small spots that can be confirmed with the naked eye on the surface of the substrate are PEDs, and when only one spot is confirmed on the surface of the substrate, it is also considered that the surface has long-period defects. Long-period defect occurrence rate (%)=(number of substrate surfaces where long-period defect occurred/20)×100 The long-period defect occurrence rate was evaluated in 5 steps according to the following criteria. That is, the larger the evaluation value, the lower the occurrence rate of long-period defects. The results are shown in Table 3. [Evaluation criteria] Long-term defect occurrence rate: Evaluation of 10% or less: "5: The occurrence is greatly suppressed, and an increase in substrate yield can be expected" More than 10% and less than 20%: "4: Actual production possible" More than 20% And less than 30%: "3: Improvement is needed in actual production" More than 30% and less than 50%: "2: Substrate yield is greatly reduced" More than 50%: "1: Far from actual production Ordinary silicon oxide abrasive grains are of the same grade)" [Measuring machine] Optical interference type surface shape measuring machine: "OptiFLAT III" (manufactured by KLA Tencor) Inner/outer radius (Radius Inside/Out): 14.87 mm/47.83 mm Center X/Y: 55.44 mm/53.38 mm Low Cutoff: 2.5 mm Inner Mask: 18.50 mm Outer Mask: 45.5 mm Long Period: 2.5 mm Wa Correction (Correction): 0.9 Rn Correction (Correction): 1.0 No Zernike Terms (No Zernike Terms): 8

[Evaluation method of alumina residue] The surface of each polished substrate was observed with a scanning electron microscope (manufactured by Hitachi, Ltd.: S-4000) at a magnification of 10,000, and the following three-step evaluation was performed. A: No aluminum oxide residues were observed on the surface B: Some aluminum oxide residues were observed on the surface C: Aluminum oxide residues were observed on the surface

7. Results Table 3 shows the results of each evaluation.

[table 3]

For example, comparing Example 2 with Comparative Example 2, as shown in Table 3, the precipitation rate of the silicon oxide slurry in Example 2 becomes significantly smaller than that of the silicon oxide slurry in Comparative Example 2, and by The redispersibility of silicon oxide particles is improved by containing a redispersibility enhancer. The same applies to the comparison between Example 1 and Comparative Example 1, and Example 6 and Comparative Example 3.

Also, in the case of using the abrasive composition prepared using the silicon oxide slurry immediately after production, although there was no significant difference in the polishing speed between Example 2 and Comparative Example 2, when the abrasive composition was used and used statically after production In the case of the abrasive composition prepared from the silicon oxide slurry after 3 months, the grinding speed in Comparative Example 2 was significantly reduced, but it was basically unchanged in Example 2. Also, when using the abrasive composition prepared by using the silicon oxide slurry that was left to stand for 3 months after manufacture, the occurrence rate of long-term defects in Example 2 was significantly lower than that in Comparative Example 2. The same applies to the comparison between Example 1 and Comparative Example 1, and Example 6 and Comparative Example 3.

In the silica slurry of Comparative Example 5 using PEG (weight average molecular weight: 6,000), which is widely known as a dispersant, the redispersibility of the silica particles was poor. In Comparative Example 6, by using PEG with a larger weight average molecular weight, the evaluation of redispersibility became good, but the grinding speed was slow. The polyacrylic acid-based carboxylic acid-based polymer used to prepare the silicon oxide slurry of Comparative Example 7 does not meet the alkali viscosity-enhanced polymer emulsion.

As shown in Table 3, the silicon oxide slurries of Examples 1-14 containing the alkali-adhesive polymer emulsion as a redispersibility enhancer were compared with those of Comparative Examples 1-4 that did not contain the alkali-adhesive polymer emulsion. Compared with silicon oxide slurry, the redispersibility of silicon oxide particles after long-term storage is excellent. Moreover, compared with the polishing liquid compositions 15-21, the polishing liquid compositions 1-14 prepared by using the long-term stored silicon oxide slurries of Examples 1-14 can ensure high polishing speed and reduce long-term defects. [Industrial availability]

According to the present invention, even after long-term storage, it is possible to ensure a high polishing rate and to suppress degradation of substrate quality such as long-period defects, so that the productivity of manufacturing a magnetic disk substrate with good substrate quality can be improved. The present invention can be preferably used for manufacturing magnetic disk substrates.

Claims (13)

A method for producing a polishing liquid composition, which includes the steps of mixing a silicon oxide slurry and an acid for the polishing liquid composition, and setting the pH value at 25°C to 0.5 or more and 6.0 or less, wherein the polishing liquid The silicon oxide slurry for the composition contains silicon oxide particles, a redispersibility improving agent, and water. The above redispersibility improving agent is an alkali thickened polymer emulsion. The above silicon oxide slurry for the polishing liquid composition is The pH value is not less than 8.0 and not more than 12.0, and the viscosity of the silicon oxide slurry for the polishing liquid composition at 25° C. is not less than 20 mPa‧s. The method for producing a polishing liquid composition according to claim 1, wherein the content of silicon oxide particles in the silicon oxide slurry for the polishing liquid composition is 10 mass % or more and 70 mass % or less, and water is further mixed in the above step . The method for producing a polishing liquid composition according to claim 1 or 2, wherein the viscosity at 25° C. is 10 mPa‧s or less when the pH value is set at 0.5 to 6.0. The manufacturing method of the polishing liquid composition according to claim 1 or 2, wherein the above-mentioned redispersibility improving agent is an alkali thickening type carboxylic acid polymer. Such as the manufacturing method of the polishing liquid composition of claim 1 or 2, wherein the above-mentioned silicon oxide particles contain There are non-spherical silicon oxide particles. The method for producing a polishing liquid composition according to claim 5, wherein the average secondary particle size of the above-mentioned non-spherical silicon oxide particles is not less than 150 nm and not more than 580 nm. The method for producing a polishing liquid composition according to claim 1 or 2, wherein the above-mentioned polishing liquid composition is an abrasive composition for magnetic disk substrates. A silicon oxide slurry for a polishing liquid composition, which contains silicon oxide particles, a redispersibility improving agent, and water, and the redispersibility improving agent is an alkali viscosity-enhancing polymer emulsion, and the polishing liquid composition uses a silicon oxide slurry The pH value of the slurry at 25°C is not less than 8.0 and not more than 12.0, and the viscosity of the silicon oxide slurry for polishing liquid composition at 25°C is not less than 20mPa‧s. A silicon oxide slurry for a polishing liquid composition, which contains silicon oxide particles, a redispersibility improving agent, and water, and the redispersibility improving agent is an alkali viscosity-enhancing polymer emulsion, and the polishing liquid composition uses a silicon oxide slurry When the pH value of the slurry at 25°C is 8.0 to 12.0, the viscosity of the silicon oxide slurry for polishing liquid composition is 20mPa‧s at 25°C, and the pH value is set to 0.5 to 6.0 The viscosity of the silicon oxide slurry for polishing liquid composition at 25° C. is 10 mPa‧s or less. A polishing liquid set, which contains the silicon oxide slurry (first liquid) for the polishing liquid composition according to claim 8 or 9, and is housed in another container different from the above silicon oxide slurry for the polishing liquid composition An acidic aqueous solution (second liquid) having a pH of 0.5 to 6.0 at 25°C when the first liquid and the second liquid are mixed. A method for manufacturing a magnetic disk substrate, comprising the step of polishing a substrate to be polished with a polishing liquid composition for a magnetic disk substrate prepared using the silicon oxide slurry for a polishing liquid composition according to claim 8 or 9. The method for manufacturing a magnetic disk substrate according to claim 11, wherein the above-mentioned substrate to be polished is an aluminum alloy substrate coated with Ni-P. A method for polishing a substrate, comprising the step of polishing a substrate to be polished using a polishing composition prepared from a silicon oxide slurry for the polishing composition according to claim 8 or 9, and the above-mentioned substrate to be polished is used for Substrates for manufacturing disk substrates.